In: Mechanical Engineering
Answer to the following:
a. Define the flow work from the energy balance for the control volume system.
b. What is the flow work for the case of steady, incompressible flow?
c. Discuss the physical meaning of the equation for the above case b.
d. Discuss the reason why the flow work of a heat pump must be minimized.
e. Discuss which process is the best for a heat pump among the isentropic, polytropic, and isothermal processes in terms of the P-v property diagram
Please note: Images a,b,c, and e are related to the respective part of the answer.
(a)FLOW WORK
Amount of work required to make the mass flow in or out of the control volume is called open system work or flow work or Flow Energy.. Flow work ensures continuous flow in and out through control volume.
(b)FLOW WORK FOR STEADY, INCOMPRESSIBLE FLOW
Flow work in case of steady and incompressible flow is given using SFEE.
(c) PART C has been solved in image
(d)The pump is a work consuming device, It needs energy in to do the work. In case of heat pump work input is kept as low as possible to maintain decent efficiency. Many times increased work is because of irreversibilities such as friction.
(e)A heat pump is a steady flow device which loses heat but in the assumption, it is assumed to be an isentropic process where no heat transfer takes place an entropy remains constant and work transfer occurs in absence of friction.